Catalytic polymerization of hydrocarbons



ate-sea a. 1, 1950 CATALYTIC POLYMERIZATION OF HYDROCARBONS George R.Bond, Jr., Paulsboro, N. J., and George Alexander Mills, Swarthmore,Pa., assignors to Houdry Process Corporation, Wilmington, Del., acorporation of Delaware No Drawing. Application October 15, 1947, SerialNo. 780,108

3 Claims.

In our copending application Serial No. 651,426, Patent No. 2,449,050,filed March 1, 1946, of which the present application is acontinuation-in-part, certain novel hydrocarbon conversion processes aredescribed in which cerium phosphate is employed as catalyst. The presentapplication is directed particularly to the use of cerium phosphatecatalysts for polymerization of hydrocarbon fractions containing lowmolecular weight olefins, particularly C3-C5 olefins, to produce chieflypolymeric hydrocarbons containing about 6 to 12 carbon atoms.

In accordance with the invention, a hydrocarbon fraction containing suchlow molecular weight olefins, more particularly one containing butenesand propenes, is contacted with cerium phosphate under conditions toeffect polymerization of these chiefly to Ce-Ca polymers. Theseconditions generally involve temperatures in the range of about 250 to500 F., preferably from about 300 to 450 F. and superatmosphericpressures to maintain the charge in liquid state or at least in a densegaseous state approaching the density of the liquid state. Pressures upto 2000 pounds per square inch can be employed, but from the standpointof equipment particularly, it is preferred to operate at somewhat lowerpressure as in the range of 500 to 1200 pounds per square inch.

As readily available charge stocks which are polymerizable by theprocess of the present invention there may be employed low molecularweight olefinic hydrocarbons or normally liquid or gaseous mixturescontaining these and saturated hydrocarbons, such as light ends from thecracking of petroleum hydrocarbons, products from gas-making processesand by-product gasses from butadiene dehydrogenation. For the productionof polymer gasoline of high quality useful for blending with straightrun gasoline to increase its anti-knock value, it is preferred to employcharge stocks containing at least 20% by volume of propenes and/orbutenes. Steam may be added to the charge, if desired.

The polymerization reaction in the presence of cerium phosphate catalystcan be carried out at high space rates in the order of to or morevolumes of charge (as liquid) per volume of catalyst per hour, and maybe continued over long periods, in excess of 24 hours, without requiringrejuvenation of the catalyst as by steam hydration or otherwise tomaintain its activity. Cerium phosphate is stable to regeneration athigh temperatures, and any carbonaceous deposit formed duringpolymerization can be readily removed by burning the same periodicallyas required, with oxygen-containing gas. Regeneration temperatures of750-1100 F. can be safely employed without adverse effect on thecatalyst,

and requires only a short time, of about an hour or less, after whichthe catalyst can again be directly used for further polymerization ofolefins,

The cerium phosphate catalysts employed in accordance with the presentinvention are in general produced by the interaction in aqueousmenstruum of a compound of cerium and a phosphate, including in thelatter term hydrogen phosphates, commonly known as phosphoric acids.Advantageously the cerium compound employed is a fairly soluble ceroussalt such as the acetate, chloride or sulfate. Alternatively, aninsoluble compound such as the trior tetravalent oxide or hydroxide maybe employed in dispersed form for reaction with the phosphate. Likewise,soluble phosphates are preferred such as alkali metal or ammoniumphosphate as such, or the same may be formed in the reaction mixtureemploying for instance ortho or meta phosphoric acid and an alkalinereacting salt or base. The cerium phosphate formed, depending upon thespecific reactants employed and the concentrations, may be a precipitateor a gel.

The cerium phosphate may be washed free or susbtantially free of othercations and anions if desired and is preferably dried prior to washing.In accordance with a preferred form of the in vention, the ceriumphosphate is formed into pellets or other discrete pieces in any knownor desired manner and the obtained pieces calcined at elevatedtemperature at above 500 F. For instance the washed or unwashed productmay be filtered and partially dried to form a cake which can be brokenup to lumps of suitable size or the same may be cast or extruded topieces of desired size and shape with adjustment of the water content toproper advantage for the particular forming process employed; that isthe wet product may be reduced in water content or water added to thedried product as required.

Although the contact material is referred to herein as cerium phosphatefor convenience, it cannot be definitely asserted that the masscomprises a combination of cation and anion or comprises a plurality ofoxides. Apparently even though precipitating reactions to form theproduct involve stoichiometric ratios, such ratios may not be retainedon calcination, in fact there are some indications that dissociationdoes occur at least in part at these high temperatures. The inventionaccordingly is not limited to any partic ular salt structure orcomposition but includes the products of interaction of the stated typesof reagents, yielding products consisting essentially of combinations ofcerium, phosphorus and oxygen, which are herein referred to forexpedience as cerium phosphate.

Although the cerium phosphate requires no support and can be used ascatalyst in granule or lump form or more regular shaped masses. it iswithin the-scope oi the present invention to employ contact masses inwhich the cerium phosphate is deposited or precipitated in or on asuitable support or carrier, which may be comparatively inactive such askieselguhr, iullers earth or bauxite, or an earth or clay having more orless catalytic activity such as a kaolin or an acidactivated bentonite,or a synthetic gel such as silica or silica-alumina.

The cerium compound employed in the reactions above designated need notbe a pure compound, so long as metals or compounds deleterious tocatalytic polymerization, are kept at a minimum. Naturally occurringrare earth minerals rich in cerium offer a convenient source for thecerium product to be combined with the phosphate. The naturalcerium-containing earth may be extracted with an acid such as sulfuric,or rare earth oxides and related metal oxides in admixture from anatural earth may be dissolved in other solubilizing acids such asacetic. The acid liquor containing cerium and other rare earth and 1*"closely allied salts may then be precipitated with an alkalinephosphate. Undesired metal compounds may be conveniently removed fromthe acid liquor previous to phosphate formation by selective orfractional precipitation with suitable reagents.

Monazite, which contains cerium compounds as the principal rare earthmetal compound present, with lesser portions of thorium compounds andother rare earth compounds, has been iound an excellent startingmaterial for the preparation of cerium phosphate containing catalysts.The monazite may be extracted with mineral acid and the mixed cerium andother rare earth salts and thorium salts so formed may be precipitatedas phosphates in mass or deposited on a suitable carrier. Alternatively,of course, one or more of the metal salts present in the acid liquor maybe selectively removed; for instance, thorium can be removed by hotprecipitation with NazSzOa. Since monazite contains the rare earth metalcompounds in natural state chiefly as phosphates, the invention alsoincludes the use of the natural earth per se in hydrocarbon conversionprocesses of the types herein designated, as well as contact masses inwhich the monazite is admixed with or deposited on a suitable matrix orcarrier such as silica gel or clay.

Various specific embodiments for preparation of cerium phosphatecatalyst are illustrated in the following examples.

Example I Two solutions were prepared, one by dissolving 115 parts 01'cerium nitrate in 1580 parts of water. The second solution was preparedby dissolving 91.5 parts of mono-ammonium phosphate (NH4H2PO4) in 1680parts of water and 63 parts of 28% aqua ammonia added thereto. Thesecond solution was poured into the first and about 9 parts ofphosphoric acid (1131 04) added with agitation. A gel was formed at 7.2pH. (Above proportions are given by weight).

The gel above formed was allowed to stand for one hour, then filteredand dried at 250 F. with circulation of air through the gel. The driedgel, which was a hard, dark brown, granular product, was water washeduntil tree 01 NO: and Ce; at this stage only traces of P04 were testedin the wash water. The washed gel was pan dried at 250 F. and formedinto 6 mm. pellets, which were calcined in air at 1050 F. for 2 hours.

The calcined catalyst is fairly hard and thermally stable, and thereforecan be employed over long;v periods without excessive losses due toattrition and volatilization.

A phosphate catalyst may be similarly prepared by employing a mixture ofsoluble rare earth salts such as acetates predominating in ceriumacetate instead of the cerium nitrate.

Emmple II Monazite sand was digested with concentrated sulfuric acidwith stirring over a period of three hours at a temperature just belowboiling, then cooled and poured into water. The residue was furtherextracted with water until no more dissolved.

Sodium silicate diluted with water was added to the above solution incalculated proportions to obtain S102 by weight to 10% oithe driedphosphate weight and aqueous ammonia added to pH 8. The mass set to afirm gel in about five seconds, which was permitted to stand for an Thegel was granulated and dried at 180 200 F., then washed with water andammonium chloride solution a number of times to remove sodium ions and aain dried.

The dried product was ground and made into a smooth paste which was castinto 4 mm. pellets. The pellets were dried at 105 C. and calcined forfive hours at 1400 F. in air containing 6.5% by weight of steam.

As an example of depositing 9. natural phosphate on a carrier, monazitesand as a fine powder may be batched with about four times its weight ofkaolin or other clay and water added to make a thick paste. A smallamount of kerosene or gas oil mixed into the paste will assist extrusionof the paste into rods which can be broken up into catalyst pellets.

Example III The catalyst of Example I was employed in the polymerizationof an olefin containing charge of the following composition;

Component incl per cent Wt. per cent The charge was introduced into areactor containing a fixed bed of the catalyst at a space rate of 10volumes (liquid at 60 F.) of charge per volume of catalyst per hour, andpolymerized under pressure 01' 600 pounds per square inch gage, during aperiod of four hours at each of the temperatures indicated in thefollowing table. The yields are shown in the table.

Avg. bed temp., F 325 400 305 Conv. mol per cent:

Total unsats 55.2 39.4 48.8 Iso-butylene 88.8 61.0 81.9 n-butylene 3.820.7 19.7 Product insp.:

Gravity, API 71.5 71.9 65.1 ASTM dist.-

Int., vol. per cent 86 87 89 5 90 95 131 97 103 170 113 120 220 140 145231 192 187 239 229 218 249 248 227 266 279 238 314 351 260 350 432 350Obviously many modifications and variations of the invention ashereinbefore set forth may be made without departing from the spirit andscope thereof and therefore only such limitations should be imposed asare indicated in the appended claims.

We claim as our invention:

1. The method of selectively polymerizing isobutylene to polymersthereof boiling essentially in the range of gasoline, which comprisessubjecting a low molecular weight hydrocarbon charge comprisingisobutylene to contact with an adsorptive contact mass containing ceriumphosphate as the sole component thereof having catalytic polymerizingactivity, at a temperature of 250-500 F. and under pressure at leastsufllcient to maintain the hydrocarbon charge in liquid state.

2. The process in accordance with claim 1 in which the temperature ismaintained within the range of 300-450" F. and the pressure within500-1200 pounds per square inch gauge.

3. The process in accordance with claim 1 in which said adsorptivecontact mass consists essentially of cerium phosphate.

GEORGE R. BOND, JR. GEORGE ALEXANDER MILLS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,813,478 Andrussov et al July'7, 1931 2,336,793 Layng et a1 Dec. 14, 1943 FOREIGN PATENTS NumberCountry Date 316,945 Great Britain Aug. 14, 1930 OTHER REFERENCESBerkman et al., Catalysis, page 961, Reinhold Publ. Corp. (1940).

1. THE METHOD OF SELECTIVELY POLYMERIZING ISOBUTYLENE TO POLYMERSTHEREOF BOILING ESSENTIALLY IN THE RANGE OF GASOLINE, WHICH COMPRISESSUBJECTNG A LOW MOLECULAR WEIGHT HYDROCARBON CHARGE COMPRISINGISOBUTYLENE TO CONTACT WITH AN ADSORPTIVE CONTACT MASS CONTAINING CERIUMPHOSPHATE AS THE SOLE COMPONENT THEREOF HAVING CATALYTIC POLYMERIZINGACTIVITY, AT A TEMPERATURE OF 250-500*F. AND UNDER PRESSURE AT LEASTSUFFICIENT TO MAINTAIN THE HYDROCARBON CHARGE IN LIQUID STATE.